1. Field of the Invention
The present invention relates to a lockup device for a fluid-type torque transmission device, and more particularly relates to a lockup device having a plurality of friction faces.
2. Background Information
A torque converter is a known fluid-type torque transmission device. A torque converter has three kinds of bladed wheels (an impeller, a turbine, and a stator) in its interior, and transmits torque via hydraulic fluid in its interior. Such torque converters are usually equipped with a lockup device.
A lockup device is disposed in the space between the turbine and a front cover in a fluid chamber formed by the turbine and the front cover, and is a mechanism for directly transmitting torque from the front cover to the turbine by mechanically linking the front cover and the turbine.
This lockup device usually has a disk-shaped piston and a damper mechanism that elastically links the piston and the turbine in the rotation direction. The damper mechanism has a retaining plate fixed to the piston, a first spring supported by the retaining plate, a pair of intermediate plates rotatably provided with respect to the piston, a second spring supported by the pair of intermediate plates so as to act in series with the first spring, and a driven plate fixed to the turbine (see, for example, Japanese Patent No. 3,752,404).
When the lockup device is engaged, a change in hydraulic pressure moves the piston to the front cover side, and the piston slides with the front cover. As a result, torque is transmitted from the front cover to a friction plate, and is then transmitted through the damper mechanism to the turbine.
Meanwhile, when the lockup device is disengaged, a change in hydraulic pressure moves the piston to the turbine side, and the piston is able to rotate with respect to the front cover. As a result, torque does not go through the lockup device, and is instead transmitted through the fluid from the impeller to the turbine.
With this lockup device, the second spring is supported by the pair of intermediate plates. The pair of intermediate plates and the second spring is disposed in the axial direction between the turbine and the piston, and the driven plate fixed to the turbine is disposed in the axial direction between the pair of intermediate plates. Therefore, a conventional lockup device tends to be large in the axial direction.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved lockup device, and fluid-type torque transmission device having the lockup device. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.